Search PubMed⌕ Search

Biomedical subjects

K Straub

Publications and source records attributed to K Straub.

At least 37 records · Page 2Linked to original sources
PubMed1994

Production, purification, and characterization of human matrilysin (PUMP) from recombinant Chinese hamster ovary cells.

A process for semicontinuous production of matrilysin zymogen secreted from recombinant Chinese hamster ovary (CHO) cells was developed. The zymogen was purified to apparent homogeneity by sequential ion-exchange and metal chelation chromatography. These processes were scaled-up to purify gram quantities of the zymogen. The N-terminus of the secreted zymogen from the recombinant cells was the same as the observed sequence of the zymogen from natural sources. Furthermore, activation and autocatalysis of the recombinant zymogen resulted in a form with an N-terminus identical to that of the corresponding native enzyme. The three C-terminal amino acids of both the recombinant zymogen and the corresponding smaller activated form were missing. Activated matrilysin was shown to have activity against a synthetic peptide substrate. The large quantities of matrilysin that can be produced and purified from the recombinant CHO cells will be useful in determination of the structure of matrilysin.

Amino Acid Sequence↗
PubMed1991

Physicochemical characterization of recombinant human nerve growth factor produced in insect cells with a baculovirus vector.

Recombinant human nerve growth factor (rhNGF) secreted by insect cells was purified by ion-exchange and reversed-phase chromatography to near homogeneity. The N-terminus of the secreted molecule was analogous to that of mouse salivary gland NGF. In its native conformation, the insect cell produced rhNGF molecules were homodimers consisting of 120 amino acid polypeptide chains. Mature rhNGF was found not to be significantly glycosylated (less than 0.08 mol of N-acetylglucosamine/mol of protein). The rhNGF was homogeneous with regard to molecular weight and amino acid sequence. Isoelectric focusing resolved the rhNGF into one major and one minor component. Because rhNGF from insect cells can be obtained in large quantities, purified to near homogeneity, and is similar to natural NGF with regard to physicochemical properties and biological activity, it is suitable for further evaluation in animal models as a therapeutic molecule for neurodegenerative diseases such as Alzheimer's disease.

Amino Acid Sequence↗
PubMed1990

High-performance liquid chromatographic (HPLC) and HPLC-mass spectrometric (MS) analysis of the degradation of the luteinizing hormone-releasing hormone (LH-RH) antagonist RS-26306 in aqueous solution.

The kinetics of the degradation of an LH-RH antagonist, RS-26306,1, in aqueous solution from pH 1 to pH 11 were studied by reverse-phase HPLC. The pH-rate profiles at 50, 60, and 80 degrees C were U-shaped with the rate law of kobs = kHaH + kw + kOHaOH. The predicted 25 degrees C shelf life at the pH of maximum stability, pH approximately 5, is greater than 10 years. The products from the degradation were analyzed by HPLC-MS using thermospray ionization. Below pH 3, the primary product, 2, forms from the acid-catalyzed deamidation of the C-terminal amide. Above pH 7, epimerization of the individual amino acids is the principal reaction. Between pH 4 and pH 6, intramolecular serine-catalyzed peptide hydrolysis becomes important, yielding a tripeptide, 3, and a heptapeptide, 4. At the pH of maximum stability all three pathways for degradation are observed.

Chemical Phenomena↗
PubMed1986

High sensitivity assay for the alpha 2 antagonist 6-chloro-3-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine and its desmethyl metabolite in plasma using gas chromatography mass spectrometry with ammonia/CCl4 chemical ionization.

A rapid and highly sensitive assay for quantifying the alpha 2-adrenoceptor antagonist SK&F 86466 and a desmethyl metabolite has been developed, using capillary column gas chromatography/chemical ionization mass spectrometry. This assay uses deuterium-labeled analogs of the analytes as internal standards, and has a lower limit of quantification of 100 pg ml-1. A novel reagent gas, consisting of carbon tetrachloride in anhydrous ammonia, was used to achieve maximal sensitivity.

Adrenergic alpha-Antagonists↗
PubMed1986

Functional group metabolism of dopamine-2 agonists: conversion of 4-(2-di-n-propylaminoethyl)-2-(3H)-indolone to 4-(2-di-n-propylaminoethyl)-7-hydroxy-2-(3H)-indolone.

In the previous report, we reported the results of absorption, protein binding, and pharmacokinetics of the dopamine-2 agonists (D2-agonists) 4-(2-di-n-propylaminoethyl)-7-hydroxy-2-(3H)-indolone, N-(2'-hydroxy-5'-[N,N-di-n-propylaminoethylphenyl])methanesulfonamide, and 4-(di-n-propylaminoethyl)-2-(3H)-indolone. Both phenolic compounds, 1 and 2, were subject to more rapid metabolism than the nonphenol 3. In the present study, we investigated the metabolic basis of the differences in the pharmacokinetics of these compounds. In both rats and dogs, the principal urinary metabolite of 1 and 2 was the corresponding glucuronide. In contrast, 3 was first converted to 1 which then was converted to a glucuronide. On the basis of the urinary excretion of 1 and its glucuronide after intravenous administration of 1 and 3, approximately 78% of the dose of 3 in rats and 58% in dogs was converted to 1. The depropyl analogue of 3 was identified as a minor urinary metabolite. 4-(2-Di-n-propylaminoethyl)-7-hydroxy-2-(3H)-indolone was found in the plasma of rats, dogs, and cynomolgus monkeys treated with 3. The concentration of 1 declined in parallel with that of 3 in dogs and monkeys, indicating that the true half-life of 1 is shorter than or equal to that of 3. On the basis of plasma concentrations of 1 in dogs, the apparent conversion of 3 to 1 was 9%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Morphine metabolism revisited. III. Confirmation of a novel metabolic pathway.

Previous studies have led to the partial structural characterization of a glutathionylmorphine adduct which was isolated from rat liver microsomal incubations. The formation of this adduct was shown to be catalyzed by cytochrome P-450. As an extension of this work, we have carried out similar studies with N-acetylcysteine in an attempt to obtain a product amenable to complete NMR analysis and unambiguous structure assignment. Incubation of [3H]morphine and N-acetylcysteine with microsomal preparations isolated from human and from phenobarbital-treated rats led to the isolation by HPLC of a labeled species displaying a fast atom bombardment mass spectrum consistent with the expected N-acetylcysteinyl adduct of morphine. Data obtained from the high resolution 1H-NMR spectrum of the adduct and that of synthetic 10 alpha-hydroxycodeine established the structure of the metabolite as 10 alpha-S-(N-acetylcysteinyl)morphine. The results are consistent with the biotransformation of morphine involving oxidation at the benzylic C-10 position to form an electrophilic species capable of reacting with nucleophilic thiols such as N-acetylcysteine and glutathione.

Animals↗
PubMed1985

Metabolism of leukotriene B4 in hepatic microsomes.

Leukotriene B4 was metabolized in rat hepatic microsomes to two products. Mass spectral analysis of these two metabolites indicated that the major metabolite was the 20-hydroxy metabolite while the minor metabolite was the 19-hydroxy metabolite. The formation of these metabolites required NADPH and was linear with time (20 min) and protein (1.6 mg/ml). The Km apparent and Vmax for omega hydroxylation of LTB4 was 14 uM and 0.138 nmol/min/mg protein. In contrast, the km and Vmax for omega minus one hydroxylation was 54 uM and 0.093 nmol/min/mg protein. These results suggest that omega and omega minus one hydroxylations of LTB4 may be mediated by different isozymes of hepatic P-450.

Animals↗
PubMed1984

Morphine metabolism revisited. II. Isolation and chemical characterization of a glutathionylmorphine adduct from rat liver microsomal preparations.

Incubation of tritium-labeled morphine and cold glutathione (GSH) or cold morphine and tritiated GSH with liver microsomal preparations obtained from phenobarbital-treated rats led to the identification by high performance liquid chromatography (HPLC) of a glutathionylmorphine adduct. Liquid secondary ion mass spectral analysis established the molecular weight of the metabolite to be 590 which corresponds to the mass of a mono-GSH-morphine adduct. High resolution (360 and 500 MHz) 1H-NMR experiments have led to the tentative assignment of the structure of this metabolite as 10-alpha-S-glutathionylmorphine. Based on both in vivo and in vitro data, the formation of this product appears to be mediated by cytochrome P-450 and to involve a reactive intermediate that may be responsible for the observed covalent binding of radiolabeled morphine to proteins and, at least in part, for the morphine-induced depletion of GSH in the rat.

Animals↗
PubMed1982

Psoralen-deoxyribonucleic acid photoreaction. Characterization of the monoaddition products from 8-methoxypsoralen and 4,5'8-trimethylpsoralen.

The isolation and structural characterization are described of the major monoaddition products formed in the photoreaction of two naturally occurring psoralens, 8-methoxypsoralen and 4,5',8-trimethylpsoralen, with high molecular weight, double-stranded DNA. Hydrolysis of the psoralen-modified DNA and subsequent chromatography resulted in the isolation of four modified nucleosides from each psoralen. Structural characterization was accomplished by mass spectrometry and 1H NMR analysis. The major products, accounting for 44-52% of the covalently bound psoralen, are two diastereomeric thymidine adducts formed by cycloaddition between the 5,6 double bond of the pyrimidine and the 4',5' (furan) double bond of the psoralen. A minor product, less than 2% of the covalently bound psoralen, is a furan-side adduct to deoxyuridine, derived from an initially formed deoxycytidine adduct by hydrolytic deamination. A fourth product is a thymidine adduct where cycloaddition has taken place between the 5,6 double bond of the pyrimidine and the 3,4 (pyrone) double bond of the psoralen. This pyrone-side adduct accounts for 19% of the covalently bound 8-methoxypsoralen but for less than 3% of the covalently bound 4,5'8-trimethylpsoralen. All of the isolated adducts have cis-syn stereochemistry. The stereochemistry and product distribution of the adducts are determined in part by the constraints imposed by the DNA helix on the geometry of the noncovalent intercalation complex formed by psoralen and DNA prior to irradiation.

Chromatography, High Pressure Liquid↗
PubMed1980

DNA alkylation and unwinding induced by benzo[a]pyrene diol epoxide: modulation by ionic strength and superhelicity.

Superhelical and partially relaxed DNAs of simian virus 40 were allowed to react in vitro with (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). The modified DNA contained N2 guanine and N6 adenine hydrocarbon adducts in the ratio 86:14. Superhelical simian virus 40 DNA was approximately 6% more susceptible to modification than was partially relaxed viral DNA. Counterions inhibited DNA alkylation by up to 90%, Mg2+ being 50-fold more effective than Na+. The sensitivity of covalent binding to helix stability is consistent with a reaction complex in which BaP diol epoxide is intercalated. The superhelical density of the modified DNA substrates was determined electrophoretically relative to partially relaxed standards, and an unwinding angle for the hydrocarbon adducts was calculated. The angle was dependent upon the superhelicity of the DNA molecule and ranged from 330 degrees to 30 degrees. These data indicate that the modified base pairs are disrupted and, in the presence of torsional strain, act as centers for the further denaturation of up to eight adjacent base pairs. In the absence of such strain the alkylation sites have an ordered structure, with the attached hydrocarbon probably oriented in the minor or major groove of the helix.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1977

DNA strand scission by benzo[a]pyrene diol epoxides.

Syn-and anti-benzo[a]pyrene diol epoxides elicit a concentration-dependent nicking of superhelical Col E1 DNA in an in vitro reaction monitored by agarose gel electrophoresis and electron microscopy. This strand scission represents less than 1 percent of the DNA modification by diol epoxide. Kinetic analysis implicates the formation of unstable phosphotriesters, hydrolysis of which nick the DNA.

Benzopyrenes↗
PubMed1976

Elucidation of hydrocarbon structure in an enzyme-catalyzed benzo[a]pyrene-poly (G) covalent complex.

The carcinogen, benzo[a]pyrene, was covalently attached to poly (G) by liver microsomes from rats pretreated with 3-methylcholanthrene. The complex was hydrolyzed with enzymes or base and products were isolated by Sephadex chromatography. Absorbance and fluorescence spectra of the products fit that of red-shifted pyrene aromatic system and suggest that metabolism has occurred at the 7-, 8-, 9-, and 10-positions of the hydrocarbon. Benzanthracene or chrysene fluorescence were not observed in these preparations. Benzo[a]pyrene derivatives were synthesized and purified by high-pressure liquid chromatography. Dehydration of 7,8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene resulted in the formation of small amounts of 7-oxo-7,8,9,10-tetrahydrobenzoa[a]pyrene. A 7-keto species was also observed after similar treatment of the hydrocarbon-poly(G) hydrolysis products. Evidence of dehydration at the 9,10-positions was not observed. The hydrocarbon covalently bound to poly(G) is, therefore, a derivative of 7,8-dihydroxy-7,8,9,10-tetrahydrobenzol[a]pyrene with nucleic acid substitution at C-10 or 9.

Benzopyrenes↗